Uploaded image for project: 'Documentation'
  1. Documentation
  2. DOCS-13635

Investigate changes in SERVER-47672: Add minSnapshotHistoryWindowInSeconds parameter

    XMLWordPrintableJSON

Details

    Description

      Description

      Downstream Change Summary

      Removed startup/runtime --setParameter maxTargetSnapshotHistoryWindowInSeconds=int (default: 5) Maximum target snapshot history window, in seconds
      Removed startup/runtime --setParameter snapshotWindowMultiplicativeDecrease=double (default: 0.75) Snapshot window multiplicative decrease
      Removed startup/runtime --setParameter snapshotWindowAdditiveIncreaseSeconds=int (default: 2) Snapshot window multiplicative increase, in seconds
      Removed startup/runtime --setParameter minMillisBetweenSnapshotWindowInc=int (default: 500) Minimum duration between snapshot window increment, in milliseconds
      Removed startup/runtime --setParameter minMillisBetweenSnapshotWindowDec=int (default: 500) Minimum duration between snapshot window decrement, in milliseconds
      Removed startup/runtime --setParameter checkCachePressurePeriodSeconds=int (default: 5) Check cache pressure period, in seconds

      Added startup/runtime --setParameter minSnapshotHistoryWindowInSeconds=int (default: 5) Minimum target snapshot history data to keep, in seconds. Snapshot (point-in-time) reads that read data at a version older than this will get SnapshotTooOld errors.

      Deleted metrics in the "snapshot-window-settings" subsection of the wiredTiger serverStatus section that are no longer relevant.

      • "max target available snapshots window size in seconds”
      • "target available snapshots window size in seconds"

      Add metric "minimum target snapshots window size in seconds" in the "snapshot-window-settings" subsection of the wiredTiger serverStatus section – this reports the minSnapshotHistoryWindowInSeconds configuration.

      Description of Linked Ticket

      Add a new startup and runtime server parameter minSnapshotHistoryWindowInSeconds for mongod, which is the amount of history in seconds stored by the system. Remove support for maxTargetSnapshotHistoryWindowInSeconds.

      Also remove snapshot window adjustment logic, see SERVER-31767.

      • This logic was used to dynamically change the amount of history stored to avoid cache pressure. Given durable history is available now, this is no longer needed.
      • Delete metrics in the "snapshot-window-settings" subsection of the wiredTiger serverStatus section that are no longer relevant.
        • "max target available snapshots window size in seconds”
        • "target available snapshots window size in seconds"

      Add metric "minimum target snapshots window size in seconds".

      Scope of changes

      Impact to Other Docs

      MVP (Work and Date)

      Resources (Scope or Design Docs, Invision, etc.)

      Attachments

        Activity

          People

            naomi.pentrel@mongodb.com Naomi Pentrel (Inactive)
            backlog-server-pm Backlog - Core Eng Program Management Team
            Votes:
            0 Vote for this issue
            Watchers:
            3 Start watching this issue

            Dates

              Created:
              Updated:
              Resolved:
              2 years, 50 weeks ago